Cyclic pressure switch with plural diaphrams

ABSTRACT

A liquid level sensing system comprises a pumping section with a housing across which there is stretched a flexible diaphragm dividing the housing into a pair of chambers one of which is in communication by a probe with a container such as a crank case containing oil above which there is a pulsating air pressure due to the operation of an engine or compressor. When the termination of the probe is immersed in the oil there are substantially no pressure undulations transmitted to the diaphragm, but when the oil level drops sufficiently to expose the probe termination the undulating air pressure above the oil is transferred to the diaphragm which thereby reciprocates so that the chamber at the side of the diaphragm opposite that of the probe draws in air through a valve and pumps it into an accumulator-actuator section which also comprises a housing containing a flexible diaphragm dividing it into two chambers. The pumping pulsations applied to the first chamber of this accumulator-actuator section push this diaphragm in increments of movement until it activates a switch which is connected with the ignition system of the engine to shut down the engine. In case the pumping actuations are not sustained and strong as when the duct termination is exposed to the air in the oil container, the diaphragm in the accumulator-actuator section does not move far enough to operate the switch because of a bleed which bleeds off pumped air if only a few pumping actuations occur or if the actuations are weak. In another embodiment the output of the pumping section is connected to an accumulator-actuator device comprising a diaphragm mounted to a rigid element enclosing a cavity between them in such a manner that the action of the pumping section draws air from the accumulator-actuator section so that its diaphragm is pulled inwardly to decrease the volume of its cavity. The diaphragm is connected to an arm which operates an engine shut-down mechanism. A bleed at the pumping section serves to prevent actuation of the accumulator-actuator section except in the presence of sustained, strong pumping pulses.

United States Patent I [1 1 Nelson CYCLIC PRESSURE SWITCH WITH PLURAL DIAPHRAMS [76] Inventor: Robert E. Nelson, Rt. No. 1, Box

215, Willow Springs, Rosamond, Calif. 93560 22 Filed: Sept. 10,1973 21 App1.No.:395,520

[52] U.S. Cl 200/83 Y, 200/83 Q, 200/34,

73/389 [51] Int. Cl. H0lh 35/34 [58] Field of Search 91/52; 73/389; 200/81 R,

200/83 Q, 83 R, 83 J, 83 T, 83 V, 83 U, 83 W, 34, 153 V, 61.25

' [56] References Cited UNITED STATES PATENTS 3,127,586 3/1964 Heyn 200/83 Y 3,134,332 5/1964 Nelson 417/39 3,246,094 4/1966 Zaske....... 200/83 T 3,535,479 10/1970 Smyers 200/83 T 3,784,772 l/l974 Nelson 200/83 Y Primary ExaminerRobert K. Schaefer Assistant ExaminerGerald P. Tolin Attorney, Agent, or Firm-Donald D. Mon; D. Gordon Angus Jan. 7, 1975 the operation of an engine or compressor. When the termination of the probe is immersed in the oil there are substantially no pressure undulations transmitted to the diaphragm, but when the oil level drops sufficiently to expose the probe termination the undulating air pressure above the oil is transferred to the diaphragm which thereby reciprocates so that the chamber at the side of the diaphragm opposite that of the probe draws in air through a valve and pumps it into an accumulator-actuator section which also comprises a housing containing a flexible diaphragm dividing it into two chambers. The pumping pulsations applied to the first chamber of this accumulator-actuator section push this diaphragm in increments of movement until it activates a switch which is connected with the ignition system of the engine to shut down the engine. In case the pumping actuations are not sustained and strong as when the duct termination is exposed to the air in the oil container, the diaphragm in the accu'mulator-actuator section does not move far enough to operate the switch because of a bleed which bleeds off pumped air if only a few pumping actuations occur or if the actuations are weak.

In another embodiment the output of the pumping section is connected to an accumulator-actuator device comprising a diaphragm mounted to a rigid element enclosing a cavity between them in such a manner that the action of the pumping section draws air from the accumulator-actuator section so that its diaphragm is pulled inwardly to decrease the volume of its cavity. The diaphragm is connected to an arm which operates an engine shut-down mechanism. A bleed at the pumping section serves to prevent actuation of the accumulator-actuator section except in the presence of sustained, strong pumping pulses.

31 Claims, 4 Drawing Figures Patented Jan..7, 1975 3 Sheets-Sheet 1 Patented Jan. 7, 1975 3 Sheets-Sheet 2 GAB 3E:

3 Sheets-Sheet 3 CYCLIC PRESSURE SWITCH WITH PLURAL DIAPHRAMS This invention relates to cyclic pressure responsive devices.

In my U.S. Pat. No. 3,134,332, granted May 26, 1964, there is described and claimed a liquid level regulating system in which a container partially filled with a liquid is in fluid communication with a fluid displaceable element, usually a diaphragm, by means of a ducted probe having a termination which may, or may not be below the level of the liquid. A pressure cycle present within the container activates the fluid displaceable element whenever the probe termination is above the level of the liquid and activates this element only slightly, if at all, when the probe termination is submerged. Pumping means is coupled with the fluid displaceable element to transfer liquid to the container from a reserve source of liquid whenever the probe termination is above the level of the liquid.

It is often desirable to perform other functions than merely replenishing liquid in response to the liquid level, for example, signaling the liquid level condition or the shutting down of associated equipment, such as an engine or compressor, requiring a lubricating oil system wherein the oil must be maintained at a sufficient level, whenever the liquid level drops below a specified level.

An object of the present invention is to produce a response to a cyclic pressure which may be translated to any of a variety of functions which may include an electrical, mechanical or fluid output function.

Another object is to replenish a liquid to bring the liquid to a desired level or to signal low liquid level or to shut down related equipment when the liquid level is low.

A related object is to provide for the occurrence of the response when the liquid level is at a sustained low value but not when the low level is momentary or when mere transient impulses like those due to low level may be experienced.

A sensing system according to this invention responds to undulations of gaseous pressure such as may occur in a contianer of liquid above the liquid therein. Thus it can respond to the level of a body of liquid partially filling a container which has a pressure cycle within it. A duct normally terminating below the level of liquid in the container communicates with a fluid displacement element. When the liquid level falls below the termination of the duct the pressure cycle is transmitted strongly to the fluid displacement element and causes it to reciprocate. When the termination is submerged the response of the fluid displacement element is slight. The fluid displacement element, when driven by the pressure cycle, pumps air or other gas in a series of impulses. Bleed means is provided to discriminate against weak activation. The output function of the system may be means for restoring the liquid level, signaling means, or means for shutting'down operation of associated equipment.

The present invention is carried out by provision of a pumping section which performs a substantial pumping function only when receiving pressure pulses corresponding to low liquid level in the container. The output of the pumping section may be connected to an accumulator-actuator section which accumulates pulses of pressure transmitted by the pumping system such that when sufficient pulses are accumulated it functions to actuate an output device which may comprise an indicator, a shut-down device or a liquid replenishing device.

A feature of the invention resides in provision for discriminating against casual or spurious pressure impulses from the liquid container which could cause false output signals or functions. A related optional feature resides in provision for the accumulation of sensed impulses before activation of an output. A further related feature resides in provision of means for bleeding away accumulated impulses to such degree as may be required to permit output response only to strong, steady impulses such as are present under normal conditions of activation.

An alternative feature resides in provision of an output function in the form of fluid impulses which may be delivered to a responsive device together with bleed means for the desired discrimination.

The accumulator means when used may be responsive to pressure impulses which are either positive or negative as compared with atmospheric pressure and may either be closely coupled to the primary fluid displacement from the liquid container or alternatively may be remotely coupled to the primary fluid displacement.

The bleed means may be associated directly with the primary fluid displacement means or with its output.

The output function may be self-restoring or may require re-setting, as by manual means. It may be one of a variety of possible output functions, which may include not only fluid displacement means but also mechanical or electrical signaling or actuating means.

The foregoing and other features of the invention will be better understood from the following detailed description and the accompanying drawings of which:

FIG. 1 is a cross-section view of a cyclic pressure sensing device according to this invention;

FIG. 2 is an elevation view, partially in cross-section, showing the device of FIG. 1 in operative relationship with an internal combustion engine to shut down the engine under a condition of low oil level in the crankcase;

FIG. 3 is a view, mostly in cross-section, showing another form of device according to this invention in operative relationship with an engine or compressor, arranged to create a shut-down under a condition of low oil level in the crankcase; and

FIG. 4 shows a detail of a device, partially in crosssection, which may be substituted for the shutdown mechanism of FIG. 3 for the purpose of providing oil replenishment under a condition of low level of crankcase oil.

The liquid level responsive device 10 shown in FIG. 1 of the drawings comprises a pressure sensing group of elements 11 and an accumulator-actuator group 12 and a group of elements joining them represented generally by numeral 13. In assembling the device 10 the joining or intermediate group 13 will generally be as sembled first. This comprises a dish or a cup 14 having a circular outer periphery at 15 flaring inwardly to form a flat base portion 16 with a central circular opening 17 centered at the longitudinal axis 18 of the cup, which is the longitudinal axis of the entire device 10. The flat annular portion 16 is placed against the similar flat annular portion 18 of a cup 19 similar in configuration and dimensions to cup 14 so that its outer periphery 20 is spaced apart in the longitudinal direction from outer periphery 15. The surfaces 16 and 18 of the cups are held in contact with each other by sandwiching them between a flange 21 of a thimble 22 and a retaining ring 23 placed around the stem 24 of the thimble and secured in place by swaging the end of the thimble 25 to over lie a shoulder 26 of the retainer ring. If desired, adhesive may be placed between portions 16 and 18, which will inhibit possible rotation between these parts. A porous air filter ring, or annulus 27, is fitted between the cups 14 and 19 at a position outside the members 16 and 18 and may consist of a conventional open structured filtering medium such as open urethane foam. A cylindrical screen 28 is fitted between the peripheries l and of the respective cups to protect against introduction of coarse objects or dirt and to afford mechanical protection for filter ring 27.

Retainer ring 23 is grooved at 29 to receive the inner edge of an annular flexible valve element 30. This is normally a flat sheet of resilient material such as nitrile rubber so that when its inner edge is snapped into groove 29 it is forced to assume a gently conical shape because its outer portion makes contact with a flat portion 31 of cup 14'which-is substantially perpendicular to the longitudinal axis 18 but offset from groove 29 to force the resilient ring to its conical shape. Another resilient valve element 32 similar in material and di-' mensions to element 30 is snapped into a groove 33 of the thimble and dimensioned similarly to groove 29 such that element 33 is forced to take a gently conical form by contact with valve seat 34 similar to valve seat 31 and displaced longitudinally from groove 33 in the same manner.

The space 35 between valve element 32. and portion 36 of cup 19 communicates with passages 37 and 37a passing through the wall of thimble 22 to communicate with a longitudinal bore 38 opening into region 39 at the opposite side of cup 14 from cup 19. When valve element 30 is forced away from its normal position of contact with seat 31 it also opens up into region 39.

Region 39 is further abounded by a diaphragm 40.

Diaphragm 40 is circular in form and typically made of a flexible, impermeable material such as nylon fabric coated with nitrile rubber, although it will be understood that some otherflexible' material may be used instead. At its peripheral edge diaphragm 40 is secured by clamping between a peripheral face 41 of cup 14 and a juxtaposed face 42 of a cup 43 constructed and dimensioned similarly to cup 14 and positioned relative to cup 14 so that it provides a space 44 between the diaphragm 40 and the inside surface of cup 43 somewhat similar to space 39. The clamping of the periphery of the diaphragm is secured by crimping the peripheral edge of cup 43 around the peripheral edge of cup 14. Thus,.diaphragm 40 separates for the purpose of fluid displacement the space 39 generally within cup 14 from space 44 generally within cup 43.

The unit 10 will be normally supported by a nipple 45 which contains a central passage 46 providing communication between space 44 and the exterior of the unit. Threads 47 at the exterior of the nipple provide means for attaching an external supporting means.

Before clamping the diaphragm between cups 14 and 43, diaphragm plates 47 and 48 are placed on opposite sides of the diaphragm and centered at the longitudinal axis 18, and loading springs 49 and 50 are set against the respective plates. Spring 49 is supported in a recess 51 formed in ring 23 and snaps into lugs 52 formed in a circular group out of plate 47. Similar lugs 53 in plate 48 receive spring 50 which bears at its opposite end against portion 54 of cup 43 and is centered by a projection 55 of nipple 45. The plates 47 and 48, although bearing against the diaphragm, need not be secured to it as they are held approximately on center of the diaphragm by their respective loading springs.

It will usually be desirable to use both of the pair of springs and diaphragm plates with the diaphragm portion 40 when the unit is used with an engine or compressor having crankcase pressure cycles of approximately atmospheric average pressure. It is possible however to omit either one, or the other, of plates 47 and 48 and its respective spring where it may be desired to compensate for crankcase average pressures substantially greater than or less than atmospheric. Thus, whether to use both plates and springs or only one plate and spring is subject to choice and will usually be dependent on the application for which unit 10 is to be used.

The group 12 elements can be assembled in a manner similar to the assembly of the group 11 elements. Group 12 contains a diaphragm 56 of a resilient material similar to that of diaphragm 40 and is securedat its outer peripheral edge by forming or crimping the peripheral edge 57 of a cap 58 around the edge 20 of cup 19. Diaphragm 56, with cup 19, valve 32 and thimble 22 bounds a space 59. Assembled with diaphragm 56 are plates 60 and 61 held against opposite sides of the diaphragm, provided with openings at their centers which fit over a stud 62 and held against a shoulder 63 by a washer 64 secured by swaging a rim of the stud at 65 over the washer. The stud 62 contains a central longitudinal passageway 66 which provides communication between the space 59 at one side of the diaphragm and space 67 at the opposite side of the diaphragm, the space 67 being bounded by the diaphragm 56 and the cap 58. A poppet 68 has its stem inserted through a passageway 66 with its head 69 outside the passageway. The diameter of stem 68 is somewhat smaller than that of passage 66 so that fluid flow is permissible through passage 66 around the stem. The end of stem 68 opposite head 69 normally makes contact with the adjacent face 70 of thimble 22 such that the poppet head 69 is normally located some distance from face 71 of the stud 62. The poppet cannot move out of the stud 62 however, because its movement in the outward direction is restricted by the presence of an operating button or arm 72 of a switch 73. A spring 74 bears at one end against face 75 of cap 58, and at the other end against the exposed face of plate 60 and is centered around the longitudinal axis 18 by having its spiral around stud 62. The spiral spring is under a 'degree of compression which biases the diaphragm 56 towards space 59, thereby providing a type of discrimination in the operation of the unit 10, depending upon its degree of activation as is described in more detail hereinafter.

The output of the unit may be sensed in any of a variety of ways, usually involving the'movement or alteration of some element. In FIG. 1 the output is sensed by switch 73 whose arm or moving element 72 is assumed to be operable by relatively low force applied to it. The switch may, for example be a single-pole double-throw snap switch, which is a well-known type of switch needing no detailed description here. The switch may be an automatically resetting-type or it may be a manual resetting-type which is the type illustrated in FIG. 1, the operator extension arm 76 being adapted to snap the switch manually to the opposite position from that to which it is snapped when the button 72 is engaged by poppethead 69.

The unit is operable to produce an output in response to pressure undulations of sufficient amplitude and duration, but not to produce an output when there are no pressure undulations, or when the undulations are of relatively small amplitude or duration. When undulating pressure is applied at nipple 45 and hence into space 44 diaphragm 40 is acted upon to undulate accordingly, which thereby produces corresponding pressure variations in space 39. During intervals when diaphragm 40 moves toward the inlet nipple 45 pressure in space 39 becomes reduced, which opens valve 30 to draw in atmospheric air through filter 27 and ports 77 to region 78 and past open valve 30 into space 39. Upon movement of the diaphragm in the opposite direction towards space 39, the air in space 39 is compressed and the valve 30 closed, thereby forcing air from space 39 through bores 38 and through passages 37 and 37a to region 35, the pressure of which opens valve 32 to admit air into space 59 from whence the air flows through the restricted passageway between poppet stem 68 and opening 66 into region 67 from whence it readily passes to atmosphere through ports 79. If the amplitude of movement of diaphragm 40 is relatively small due to small amplitude of input undulation, the restricted bleed between poppet stem 68 and hole 66 is sufficient to bleed-off the resulting air sent into regions 59 and 67. If, however, the undulations are strong, the air is pumped into region 59 faster than it can be bled out with the result that at each pumping pulse the diaphragm 56 makes a net movement into space 67.

With a long-enough train of such pulses the continued movement of the diaphragm carries face 71 of stud 62 toward switch button 72 until head 69 of poppet 68 becomes entrapped between switch button 72 and face 71 of stud 62. At this point the bleeding of air through passage 66 ends, making further pumped increments of air into space 59 completely available to drive forward diaphragm 56 and thus face 71. Movement then proceeds rapidly and forcefully to set switch 73 through button 72.

From the foregoing, it will now be seen that even one or two relatively strong impulses from the primary or pumping section 11 will be insufficient to set switch 73 unless immediately followed by further pulses; if not, the bleeding of air through passage 66 will promptly allow spring 74 to restore diaphragm 56 to its normal position and no output function will result.

FIG. 2 illustrates a specific example of the use of a unit according to FIG. 1 in a system for providing low oil level protection for an engine or compressor. In FIG. 2 there is shown a single-cylinder internal combustion engine 80 having a cylinder 81 containing a piston 82 with a connecting rod 83 operating a crank 84 on a crankshaft with a spark plug 85 mounted on cylinder head 86. A magneto 87 is used to fire the spark plug over an electrical line 88 at times related to the position of piston 82 in its cycle as determined by a timer which properly energizes the magneto, such timing means being common equipment. It is not illustrated. The engine'is assumed to be cooled by a cooling means 89 ordinarily comprising a storage facility for a cooling fluid and a radiator for cooling it which circulates the cooling fluid through a cooling fluid channel 90 related to the cylinder wall. The engine is shown with the usual crankcase 91 resting on a sump 92 constructed as a lower extension of the crankcase. According to common practice, the sump contains a supply of lubricating oil 93 which for good and safe operation of the engine should be maintained between a full level indicated by broken line 94 and a low or cut-off level indicated by broken line 95.

A probe 96 in the form ofa hollow tube extends into the crankcase and sump from a position outside the crankcase where it is secured in a suitable manner as by brazing to a plate 97 attached to the exterior of the crankcase. Outside the crankcase th probe 96 is connected to a hose 98 by a clamp 99, the other end of the hose being clamped to a nipple 100 attached to a coupling 101 threaded to the nipple 45 of unit 10. The coupling 101 is fastened to a bracket 102 secured to the wall of the crankcase 91. The inner end 103 of the probe 96 may be left open if desired, or alternatively it may be closed by a plug 104 in which case a port 105 must be provided behind the plug to provide communication between the interior of the probe and the interior of the crankcase sump.

According to conventional practice the magneto 87 is provided with a grounding terminal 106 which in effect short circuits the magneto to terminate ignition of the spark plug whenever the grounding terminal is grounded to the engine. To provide for thus grounding the magneto at desirable times a conductor 107 is connected between terminal 106 and a terminal 108 of switch 73. Another terminal 109 of switch 73 is grounded to the motor by conductor 110 which is connected at 111 to the bracket 102 fastened to the crankcase. When switch contact points 112 and 113 are out of contact with each other as shown in FIG. 2 the magneto is ungrounded. But, when contacts 112 and 113 are brought together by actuation of switch 73 the magneto becomes grounded and ignition is terminated.

During the running of the engine, piston 82 sequentially moves into and out of crankcase 91 to compress and decompress the gases therein alternately, resulting in pressure undulations within the crankcase of sufficient intensity to activate unit 10 by sustained reciprocation of its diaphragm 40 over a sufficient time period as has been explained heretofore. A breather 114 comprising a hollow nipple 115 provided with a seat 116 on which a ball 117 loaded by a spring 118, seats, providing for venting crankcase gases to tmosphere through passages 119 formed in cap 120 of the breather. This provides an average pressure reference to atmosphere for the gases within the crankcase. In the form of breather illustrated, peaks of pressure within the crankcase which slightly exceed atmospheric pressure cause ball 117 to lift from seat 116 against light pressure from the spring 118, thereby permitting gas passage through passage 119. With this form of breather, average pressure of the crankcase is usually negative with respect to atmosphere.

There are many engines and compressors which do not use a breather valve as illustrated and described in FIG. 2 but, instead, simply breathe limited amounts of gases on each cycle to atmosphere, which can be achieved by a breather such as 114 if the ball and spring be omitted. In such case, the breather simply serves as a restricted means of venting the crankcase to atmosphere and creates within the crankcase an average pressure either substantially atmospheric, or if engine blow-by passed by piston 82 be strong, may be somewhat positive. Regardless of which form of breather is used, the amount of gases passing between the crankcase and atmosphere during a single-engine cycle will not be great enough to affect materially the amplitude of the crankcase cycle within the range of speeds in normal operation of the engine.

When the port 105 of the probe (or the end 103 of the probe in case there is no plug 104 or port 105) is immersed, as is the case whenever the oil level in the sump is above the cut-off level 95, some oil will ultimately move into the probe through the port during the more positive parts of the pressure cycle and move out of it during the more negative parts. The air displacement within the probe resulting from this in-and-out movment of oil is communicated from the probe through the hose 98 to diaphragm 40 within unit 10. The relatively small amount of displacement due to this in-and-out'movement of oil to and from probe 96 will be incapable, during normal engine operation, of being in sufficient volume during a pressure cycle to produce more than a moderate disylacement of volume within the probe and therefore will be incapable of producing a substantial displacement of diaphragm 40.

When however, the port 105 is no longer immersed in oil, as will occur when the level of the oil within the crankcase or sump has been depleted to become below that of port 105 the port 105 is no longer greatly restricted in its capacity to pass substantial volumes of fluid into it, which in this case, is the gas within the crankcase above the oil. Thus, there is a substantial volume of gas into-and-out-of the probe in this case, which produces a corresponding substantial displacement of diaphragm 40. This ability to discriminate between oil, providing little volume of flow through port 105 during a cycle, and the gases of the crankcase, producing relatively high volume of flow during a cycle, occurs because of the very great difference between the density of oil and that of crankcase gases. Thus, typically, the ratio of potential flow of gasesto potential flow of oil, assuming the probe to be open to one or the other, is in the general order of about 30 to 1, providing an ample basis for discrimination by unit 10.

Any substantial movement of diaphragm 40 results in pumping of air from the atmosphere into space 39 and delivery of air through passages 38, 37, 37a into space 59 as described heretofore. From space 59 the air may either displace diaphragm 56 into space 67 against the force of spring 74 or else pass through passage 66 into space 67 and out through ports 79 as described heretofore.

From the foregoing, it is observed that when the movement of diaphragm 40 is slight or even nonexistent, as will be the case when port 105 of the probe is immersed in the oil, little or no air will be pumped into space 59. When the delivery of air into space 59 is low, passage 66 is sufficiently large to pass this air without development of sufficient pressure in space 59 over that prevailing in space ,67 to cause the assembly of diaphragm 56 to move in opposition to spring 74. Thus, immersion of port 105 in the oil prevents development of any movement of the diaphragm assembly 56.

When however, port 105 ceases to be immersed in oil and becomes open to gases of the crank case, the

pumping action of diaphragm 40 becomes strong, causing relatively large volumes of air to be pumped into space 59. In this case, the rate of delivery of the air through passage 66 must-increase until the pressure difference across diaphragm 56 becomes great enough to overcome spring 74. The assembly of diaphragm 59 now moves towards space 67 closing the distances between face 71 of stud 62, head 69 of the poppet and switch button 72, at which time the poppethead closes passage 66 except for the very small bleed channel 26a formed in face 71 to permit later return of diaphragm 56 to its original position after cessation of air pumping, but insufficient to affect appreciably the degree of closure of passage 66 afforded by poppet 29.

With the by-passed delivery of passage 66 now virtually eliminated by contact of the poppethead 69 with face 71, most of the air pumped into space 69 becomes available to drive the diaphragm assembly 56 forward so that the poppethead moves against switch operator 72 under the increased pressure which follows the elimination of venting through passage 66, and thus driving switch 41 into operation to snap switch contact 113 against switch contact 112, which of course will immediately stop the engine by terminating ignition.

It will be recognized that operation of the system is not dependent upon use of the particular switch illustrated in FIG. 2, as there are many other types of switches which could be used instead. The switch, for example, may be a manual resetting type which will remain in its thrown position until later reset by an extension 76 or it may be automatically reset. In either case, resetting of the switch requires some passage of air from space 59 to permit the diaphragm 56 to return to its initial position and this air passage is afforded by the bleed channel 26a. Under most conditions of service, the automatically resetting type switch can be made to continue in its thrown position until engine shut-down is accomplished unless bleed channel 26a be made too large, because of the lock-out action of poppet 29.

The unit 10 may be used to control the oil level by replenishment of the oil instead of shutting down the engine. For example, the closing of the switch contacts of switch 41 may be used to operate a valve which permits flow from an oil supply to replenish the oil in the crankcase until it is brought up to the level required to immerse end 103 of the .probe. In such case, an automatically resetting switch will ordinarily be used.

As explained heretofore, the action of unit 10 normally requires a series of cycles in which the primary or pumping section 11 must continue its action before the secondary or accumulator-actuator section 12 may be activated, in conjunction with the bleed means, and this serves to discriminate against casual single-stroke or short-burst action of the primary section. This is useful when the unit 10 is used with an engine crankcase as illustrated in FIG. 2.lt is occasionally possible during starting and at other times that, usually because of casual entrapment of air adjacent to port 105, momentarily vigorous probe action can occur even though the port 105 be immersed in oil. With the requirement of a substantial number of closely-occurring strong pumping cycles to activate the accumulator-actuator section, the unit becomes relatively invulnerable to false action which might result in unwanted shutdown.

In FIG. 3 there is shown a liquid level responsive system which differs somewhat from the device of FIG. 1 and its installation in FIG. 2. The system of FIG.

3 is shown applied to a crankcase 126 which may be that of an engine or a compressor. A sump 127 is attached to the crankcase and the lubricating oil may be carried at various possible levels above the bottom 128,

a full level being indicated by broken line 129 and a cut-off level indicated by broken line 130 being that below which the oil should not be allowed to go. A pressure cycle is assumed to be present during operation similar to that described in connection with FIG. 2. A hollow probe 131 is fastened and passed through a plate 132 covering a port 133 through the side of the crankcase. The end of the probe within the crankcase is plugged at 134 and a port 135 just inside the plug provides communication from the inside of the probe to its exterior. The probe is positioned so that its port 135 is located at the cut-off level 130 of the oil in the sump.

The system 125 comprises a pumping unit 136 which bears some similarity to the pumping unit 11 of FIG. 1, in that it comprises a cup member 137 and a second cup member 138 having respective peripheral portions 139 and 140 juxtaposed to each other and binding between them the peripheries of a circular flexible diaphragm 141, such that the bases of the two cup members are remote from each other leaving respective spaces 142 and 143 on opposite sides of the diaphragm. The base portion 144 of cup member .137 is fastened to plate 132 of the crankcase and base 145 of cup member 138 has attached to it a valve assembly 146. Aligned holes 147 and 148 through plate 132 and base portion 144 respectively communicate with probe 131 providing communication from within the probe to cavity 142 of the pump unit 136. Diaphragm plates 149 and 150 are provided on opposite sides of the diaphragm and their curved peripheral rims contain helical springs 151 and 152, the opposite ends of which are held in place by enveloping bosses 153 and 154 on respective cup members 137 and 138. These springs perform a function similar to the springs in the pumping section of FIG. 1 in that they load the diaphragm against average crankcase pressure or vacuum. Depending upon the application with which the system is to be used either one or the other of these two sets of diaphragm plates and springs may be omitted.

The valve assembly 146 is incorporated in an extension 155 of base portion 145 of cup member 138. A bore 156 is provided along the longitudinal axis of pumping unit 136 and extends a substantial distance into the extension 155. Bore 156 communicates with passageways 157 and 158 extending from opposide sides and perpendicular to the longitudinal axis of bore 156 and these passageways 157 and 158 communicate with respective larger passageways 159 and 160. A plug 161 provided with a central passageway 162 is threaded into bore 159 and another smaller plug 163 having a central passageway 164 is threaded into plug 161.

A conduit 165 is attached to plug 163 by a coupling at 166. The face of plug 161 at opening 159 io provided with a raised annular boss 167 which serves as a valve seat for a flat valve plate 168 normally held against it by a compression spring 169.

The face of extension member 155 which faces space 160 is provided with an annular protuberance 170 serving as a valve seat for a flat valve 171 normally held against the seat by a compression spring 172. There is threaded to opening 160 a coupling 173 against which the spring 172 bears, and this coupling is provided with an internal passageway 174 aligned with passageway 158. A length of tubing 175 communicates with passageway 174 by means of a coupling at 176 and terminates to outside atmosphere.

The end of conduit 165 opposite that which is attached to coupling 163 is coupled to an accumulatoractuator assembly 177. This assembly comprises a cuplike member 178 to the circular peripheral rim 179 of which there is secured and may be sealed by a suitable adhesive or other means a resilient diaphragm member 180. The diaphragm also has a cup-like shape maintained by attachment of a circular plate 181 at its central position and a spiral compression spring 182 which engages plate 181 at one end and engages the base portion 183 of the cup member 178. Thus, the flexible diaphragm is normally positioned in its distended condition as illustrated in FIG. 3.

For the purpose of providing communication between conduit 165 and the interior space 184 bounded by the cup 178 and the diaphragm there is provided a coupling 185 which passes through the base portion 183 of the cup 178. The exterior part of the coupling has a shoulder 186 which abuts a structural member 187 mounted on a suitable support 188 and fastened to the base of the cup. The inner end of the coupling is swaged around a washer 189 at the inner surface of base portion 183. A coupling nut 190 serves to couple conduit 165 to coupling 185.

The forward face 191 of diaphragm 180 has attached to it a bracket 192 at the forward end of which there is placed a link 193 which extends forwardly to a bearing 194 which pivotally engages within it a pin 195 fastened to a crank arm 196 fastened and keyed to a shaft 197. Link 193 is slidable through a hole 198 atthe forward end of the yoke 192 so that it is free to move in wardly relative to the yoke. The inner end of the link is provided with a head 199 which prevents the link from being pulled out of the yoke and by which the link is pulled to the right when the yoke moves to the right with reference to FIG. 3, head 199 being initially separated from yoke 192 to permit initial lost motion before being engaged.

There is fitted into the wall of cap 178 a bleeder 200 comprising a plug 201 staked to the wall of cup 178 and having a passageway 202 comprising communication from the interior space 184 to a passageway 203 leading to atmosphere. A cap 204 protects the bleeder from entry of dirt.

Considering the pumping unit 136, diaphragm 141 is activated by gaseous fluid displacement through probe 131 whenever port 135 is unsubmerged by the liquid. The diaphragm reciprocates, displacing air in space 143 and causing pumping of air through the valves 168 and 171 and to atmosphere through tube 175. This pumping is caused by alternate movement of diaphragm 141 to increase the volume of space 143, causing air to be drawn from conduit 165 past valve element 168 and to space 143, and reverse movement of diaphragm 141 to deliver air from space 143 through valve element 171 to atmosphere. Whenever port 135 is submerged in the liquid, action of diaphragm 141 becomes negligible as any residual cyclical displacement is vented to atmosphere through a by-pass channel 205 which leads from space 143 to space 160, thus preventing opening of either valve 166 or 171 and hence, creating no pulse in conduit 165.

It is assumed that the crankcase. 126 is that of an engine or a compressor and is subjected to cyclical pressure as described in connection with FIG. 2, and that the system is operating with the level of the body of oil within the crankcase at some point above that of the cut-off level 130. Because port l35is then immersed in oil, very little cyclical displacement of fluid can occur into and from probe 131 for reasons explained heretofore in connection'with the system of FIG. 2. Correspondingly, even though the primary diaphragm 141 may make some cyclical movement, such movement will be slight, and any resulting small displacement of space 143 can readily vent to atmosphere throughbypass 205. Hence, no positive or negative pressures, relative to atmosphere, will be generated in space 143 sufficient to open valve elements 166 and 171, and no pulse signal will then be transmitted to conduit 165.

Now assuming that the oil level has dropped to or below the cut-off level 130, the gases of the crankcase can now reach port 135 which now can deliver their positive or negative cyclical pulses through probe 131 to diaphragm 141. Pumping displacement of space 143 now becomes substantial, resulting in actuation of valve elements 168 and 171 as the by-pass passage 205 is too small to transmit the relatively great cyclical displacements without generation of valve-opening pressures. Air is then drawn in a series of pulses from conduit 165 which, transmitting these to diaphragm 180, will'cause the forward part 191 of that diaphragm to move inwardly toward cup 178 against the force of spring 182 and begin to move yoke 192 towardengagement with end 1990f linkage 193. After such motion has progressed enough to engage head 199 with yoke 192, further motion causes shaft 197 to turn and to operate to shut down the engine or compressor in a wellknown manner.

Had the pulsing at conduit 165 been casual or momentary as can sometimes occur in the operation of engines or compressors, action of diaphragm 191 would have commenced but would then have terminated upon the cessation of pulsing before the initial lost motion between end 199 and yoke 192 had been satisfied, which would thereby permit diaphragm 191 to be returned to its initial position shown in FIG. 3 by the action of compression spring 182 and the admission of air from the atmosphere into space 184 through the bleeder 200. However, with the oil level below the cutoff level, the strong pulsing action will continue until actuation of the cut-off or shut-down means is complete.

It should be recognized thatthe structure comprising the probe 131, the pump assembly 136 and the valve assembly attached at its output side constitute a complete system which can accomplish shut-down or control in response to fluid level. Thus, the series of pulses developed as negative pressure or partial vacuum at conduit 165 can, for example, be used to activate shutdown of the Diesel engine of a locomotive in response to low oil in an air compressor'driven by that Diesel engine.

Alternatively, linkage 193 in FIG. 3 may be attached to actuate any movement translating or otherwise movable shut-down means, and of course, shaft 197 in FIG. 3 may be any conventional means for accomplishing shut-down such as a throttle shaft. In the case of an electrically driven compressor, shaft 197 may be an ac tuator of a circuit interrupting means. I

' 12 Diaphragm 180 in FIG. 2 serves not only the function of an actuating motor to move a linkage, but also acts as an accumulator of pulses in conduit as the actuating linkage 193 is adapted to permit a degree of early motion of diaphragm before linkage 193 is actuated. In that respect, the arrangement of diaphragm 180, and linkage 193 is somewhat analogous to diaphragm 56 and poppet 68 in FIG. 1.

FIG. 4 illustrates a linkage system which may be used in place of the'linkage assembly involving link 193 and arm 196 in FIG. 3. In FIG. 4 there is shown the forward end of yoke 192 of FIG. 3 to which there is engaged a rod 210 instead of linkage 193 of FIG. 3. The rod is held within the yoke by a nut 211 and washer 212, adjustable to permit a desired degree of lost motion, so that the rod is free to slide through hole 198 of the yoke but cannot be withdrawn from the yoke, this arrangement being similar to that of link 193 in FIG. 3. The opposite end of rod 210 enters a bore 213 of a valve housing 214 containing a cavity 215 into which the rod protrudes. A valve head 216 is attached to the end of the rod and provided with a conical forward surface 217 adapted to seat on an annular valve seat 218 formed around an opening 219 through a cap 220 of the valve housing. The cap has a threaded outwardly extending protrusion 221 on which there is threaded a coupling nut 222 which couples a conduit 223 to passageway 219 into the valve housing. The valve housing is provided with a protruding boss 224 through which there is a passageway 225 from the interior cavity 215 to which there is coupled by coupling nut 226 a conduit 227. A small compression spring 230 serves to maintain the valve 216 seated on its seat 218 to shut off communication between conduits 223 and 227. O-rings 228 in grooves 229 of the housing prevent leakage from cavity 215 to the exterior. 7

When there are no vacuum pulses produced in conduit 165 of FIG. 3 by actuation of the pumping-section 136, the diaphragm 180 is distended to the fullest extent as shown in FIG. 3 so that the valve 216 of FIG. 4 is seated in its normal position as shown in FIG. 4. When, however, pulsing occurs in conduit 165 the diaphragm 180 is retracted inwardly against the force of its spring 182 thereby pulling rod 210 to the right with reference to FIG. 4 and opening the valve so that fluid can flow from conduit 223 to conduit 227. In practice, conduit 223 will lead from a source of replenishment oil and conduit 227 will lead into the crankcase of the engine or compressor. Thus, this operation of the valve by pulsing in conduit 165 will permit oil to flow from conduit 223 through conduit 227 into the crankcase to raise its level to a position above the cut-off level, whereupon the pulsing in conduit 165 will cease and diaphragm 180 will return to its original distended position causing the spring 230 to seat the valve again.

As stated in connection with link 193 of FIG. 3, when rod 210 and the diaphragm 180 are in their normal position, there will be a space between the end of yoke 192 and the washer 212 so that the diaphragm 180 will undergo a traction for some distancebefore it commences to pull rod 210 to the rear to unseat the valve. FIG. 4 illustrates the condition of the diaphragm already having moved to the point where yoke 192 engages the washer ready to pull the valve off its seat. This corresponds to the condition of the diaphragm 180 in FIG. 3 which has already retracted sufficiently,

so that the yoke engages the head 199 of link 193 to commence pulling the crank arm 196.

It will be recognized that by the present invention there is provided a sensor-operated pumping unit which functions to pump impulses as its output in which the impulses are relatively strong when the oil level is low. On the other hand, when the oil level is relatively high at most only weak pulses are generated and these are suppressed by the bleed means which is provided. Such an assembly is illustrated both in FIGS. 1 and 3. It should then be recognized that the sensor pumping section 136 of FIG. 3 constitutes for this purpose a complete device having an output line 125 to which the pulses are transmitted and with which any of the conventional means for sensing pressure differences may be employed. In FIG. 3 the output line 125 is described as a vacuum line, but it will be understood that either positive or negative pressures may be provided as the output. For example, although the unit 136 of FIG. 3 as shown produces a vacuum output in conduit 125, it will be obvious that it could equally be constituted to produce a pressure output as described in the disclosureof FIG. 1.

It will be recognized that the assembly 136 in FIG. 3 corresponds in this respect with the unit 11 in FIG. 1 with the exception that in FIG. 1 the bleed means is associated with the output from the pumping chamber of section 11, whereas in FIG. 3 it is connected directly into the pumping chamber of assembly 136.

It will also be recognized that in both FIGS. 1 and 3 there is provided an accumulator-actuator in addition to the sensor-operated pumping unit, this being the assembly 12 in FIG. 1 and being the assembly 177 in FIG. 3.

It will be understood that the embodiments of the invention illustrated and described herein are given by way of illustration and not of limitation, and that modifications or equivalents or alternatives within the scope of the invention may suggest themselves to those skilled in the art.

The term output pulse or output pulse of gas as used herein means a flow in either direction and the pulse may be of a pressure which is either negative or positive relative to atmospheric pressure. The term permitting fluid flow in relation to a chamber covers a flow of fluid either into or out of the chamber, and likewise the term flow means a flow in either direction unless otherwise stated. The terms pressure pulse and pulse of pressure and the like as used in the specification and claims cover either positive or negative increments of pressure.

I claim:

1. An undulating fluid pressure responsive device comprising:

a reciprocable element having two sides maintained means for permitting fluid flow from a source of fluid into said pulse generating chamber each time the reciprocable element moves in a second of said directions;

a fluid pulse accumulating chamber in communication with said pulse generating chamber to accumulate the generated pulses;

valve means between the fluid source and the accumulating chamber preventing the return of fluid from the accumulating chamber to the fluid source;

a fluid displaceable element forming part of the wall of the accumulating chamber and bleed passageway means providing communication between said accumulating chamber and said fluid source thereby permitting flow of fluid from said accumulating chamber at a rate sufficient to prevent a substantial displacement of said displaceable element when the fluid pulse output of said pulse generating chamber is not both strong and sustained.

2. A device according to claim 1 in which:

the fluid displaceable element undergoes incremental displacements in a path of movement by the fluid pulses applied to it.

3. A device according to claim 2 in which a movable actuating member is connected to said fluid displaceable element such that a substantial degree of movement of said fluid displaceable element must take place before movement is imparted to said member.

4. A device according to claim 1 in which the means adapted to provide fluid communication comprises a duct in communication with said first side of said reciprocable element and having a termination adapted to be placed within a container holding a body of liquid and containing a gaseous fluid above the liquid subject to pressure undulations, so that the termination may or may not be submerged in the liquid.

5. A device according to claim 1 including means providing a pressure bias on at least one side of said reciprocable element.

6. A device according to claim 1 including means providing a pressure bias against both sides of said reciprocable element.

7. A device according to claim 4 in which said reciprocable element comprises a flexible diaphragm.

8. A device according to claim 7 in which said fluid displaceable element comprises a second flexible diaphragm.

9. A device according to claim 8 in which said means for permitting fluid flow from a source of fluid into said pulse generating chamber comprises a valve means which admits pulses of fluid to said pulse generating chamber when said first diaphragm reciprocates.

10. A device according to claim 9 in which a second valve means admits pulses of fluid from said pulse generating chamber into said pulse accumulating chamber.

11. A device according to claim 9 in'which said bleed means comprises an opening through said second diaphragm.

12. A device according to claim 11 in which a poppet is placed at said opening, said poppet having a head which closes said opening when the second diaphragm moves some distance in its path of incremental movement.

13. A device according to claim 11 including an element moved by said second diaphragm when its incremental movement has been sustained for a time.

and the means responding to the sustained incremental movement comprises means for terminating operation of equipment creating the undulating pressure.

15. A liquid level responsive device comprising:

a first housing;

a first flexible reciprocatable diaphragm crossing the interior of said first housing and creating a first chamber and a second chamber within the housing on opposite sides of the diaphragm;

means for introducing pulsating fluid pressures into the second chamber;

a first valve through which gas from a source of gas is introduced into the first chamber;

a second housing;

a second flexible diaphragm crossing the interior of the second housing and creating a first cavity and a second cavity on opposite sides of the second diaphragm within the second housing;

a second valve between said first chamber and the first cavity through which pulses of gas pass from the first chamber to the first cavity, said second valve preventing the return of gas from the. second cavity to the first chamber thereby causing the second diaphragm to move in one direction in a path of movement when the first diaphragm reciprocates;

an actuator movable by substantial uni-directional movement of the second diaphragm in said path of movement; and

bleed means at said first cavity for bleeding off gas therefrom, thereby preventing substantial movement of said second diaphragm when said pulsating fluid pressures are weak or unsustained.

16. A device according to claim 15 in which a fluid pressure sensing duct is in communication with said means for introducing pulsating fluid pressures.

17. A device according to claim 16 including a switch having a member operated by said actuator.

18. An undulating fluid pressure responsive device comprising:

a reciprocable element having two sides maintained out of communication with each other;

means adapted to provide fluid communication between a first of said sides and a body of fluid subject to undulating pressure which can reciprocate said reciprocable element in opposite directions, the other of said sides forming part of the wall of a fluid pulse generating chamber whose volume is changed by the reciprocation;

means for developing an output pulse of fluid pressure each time the reciprocable element moves in a first of said directions;

means for permitting fluid flow to a delivery region from said pulse generating chamber each time the reciprocable element moves in a second of said directions;

a fluid pulse accumulating chamber in communication with said pulse generating chamber to accumulate the generated pulses;

valve means between the delivery region and the accumulating chamber preventing the return of fluid from the delivery region to the accumulating chamber;

a fluid displaceable element forming part of the wall of the accumulating chamber and bleed passageway means providing communication between said accumulating chamber and said delivery region thereby permitting flow of fluid into said chamber at a rate sufficient to prevent a substantial displacement of said displaceable element when the pulse output of said pulse generating chamber is not both strong and sustained.

19. A device according to claim 18 in which:

the fluid displaceable element undergoes incremental displacements in a path of movement by the fluid pulses applied to it.

20. A device according to claim 19 in which a movable actuating member is connected to said fluid displaceable element such that a substantial degree of movement of said fluid displaceable element must take place before movement is imparted to said member.

21. A device according to claim 18 in which the means adapted to provide fluid communication comprises a duct in communication with said first side of said reciprocable element and-having a termination adapted to be placed within a container holding a body of liquid and containing a gaseous fluid above the liquid subject to pressure undulations, so that the termination may or may not be submerged in the liquid.

22. A device according to claim 18 including means providing a pressure bias on at least one side of said reciprocable element.

23. A device according to claim 18 including means providing a pressure bias against both sides of said reciprocable element.

24. A device according to claim 21 in which said reciprocable element comprises a flexible diaphragm.

25. A device according to claim 24 in which said fluid displaceable element comprises a second flexible diaphragm.

26. A device according to claim 25 in which said means for permitting fluid flow from a source of fluid into said pulse generating chamber comprises a valve means which admits pulses of fluid to said pulse generating chamber when said first diaphragm reciprocates.

27. A device according to claim 26 in which a second valve means admits pulses of fluid from said pulse generating chamber into said pulse accumulating chamber.

28. A device according to claim 26 in which said bleed means comprises an opening through said second diaphragm.

29. A device according to claim 28 in which a poppet isplaced at said opening, said poppet having a head which closes said opening when the second diaphragm moves some distance in its path of incremental movement.

30. A device according to claim 28 including an element moved by said second diaphragm when its incremental movement has been sustained for a time.

31. A device according to claim 21 in combination with a container comprising a crankcase containing oil and gas above the oil subject to undulating pressure and the means responding to the sustained incremental movement comprises means for terminating operation of equipment creating the undulating pressure.

III k l UNITED STATES PATENT OFFICE Page 1 of 2 CERTIFICATE OF CORRECTION Patent No. 3,859,484 Dated January 7, 1975 Inventor(s) ROBERT E. NELSON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[54] Title change "cYcLIc PRESSURE SWITCH WITH PLURAL DIAPHRAMS" to -CYCLIC PRESSURE ACTUATED DEVICE WITH PLURAL DIAPHRAGMS-- Col. 1, line 44 "contianer" should read --container-- Col. 3, line 41 "abounded" should read --bounded- Col. 5, line 65 change "magneto, such" to --magneto. Such- Col. 5, line 65 change "equipment. It is" to -equipment,

it is-- Col. 6, line 15 "th" should read --the- Col. 6, lines 50-51 "providing" should read --provides-- Col. 6, line 51 "tmosphere" should read -atmosphere-- Col. 7, line 24 "disylacement" should read -displacement- Col. 8, line 22 "41" should read --73-- C01. 9, line 59 "i0" should read -is-- UNITED STATES PATENT OFFICE Page 2 of 2 Patent No.

Inventor(s) Robert E. Nelson Dated January 7. 1975 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 13, line 49, after "stated." insert the following new paragraph:

[SEAL] The terms "reciprocahle" and "reciptocatable" and the like are used interchangeably to mean "reciprocative" or reciprocatory".

Signed and Sealed this Attest:

RUTH C. MASON Arresting Officer LUTRELLE F. PARKER Acting Commissioner of Patents and Trademarks 

1. An undulating fluid pressure responsive device comprising: a reciprocable element having two sides maintained out of communication with each other; means adapted to provide fluid communication between a first of said sides and a body of fluid subject to undulating pressure which can reciprocate said reciprocable element in opposite directions, the other of said sides forming part of the wall of a fluid pulse generating chamber whose volume is changed by the reciprocation: means for developing an output pulse of fluid pressure each time the reciprocable element moves in a first of said directions; means for permitting fluid flow from a source of fluid into said pulse generating chamber each time the reciprocable element moves in a second of said directions; a fluid pulse accumulating chamber in communication with said pulse generating chamber to accumulate the generated pulses; valve means between the fluid source and the accumulating chamber preventing the return of fluid from the accumulatIng chamber to the fluid source; a fluid displaceable element forming part of the wall of the accumulating chamber and bleed passageway means providing communication between said accumulating chamber and said fluid source thereby permitting flow of fluid from said accumulating chamber at a rate sufficient to prevent a substantial displacement of said displaceable element when the fluid pulse output of said pulse generating chamber is not both strong and sustained.
 2. A device according to claim 1 in which: the fluid displaceable element undergoes incremental displacements in a path of movement by the fluid pulses applied to it.
 3. A device according to claim 2 in which a movable actuating member is connected to said fluid displaceable element such that a substantial degree of movement of said fluid displaceable element must take place before movement is imparted to said member.
 4. A device according to claim 1 in which the means adapted to provide fluid communication comprises a duct in communication with said first side of said reciprocable element and having a termination adapted to be placed within a container holding a body of liquid and containing a gaseous fluid above the liquid subject to pressure undulations, so that the termination may or may not be submerged in the liquid.
 5. A device according to claim 1 including means providing a pressure bias on at least one side of said reciprocable element.
 6. A device according to claim 1 including means providing a pressure bias against both sides of said reciprocable element.
 7. A device according to claim 4 in which said reciprocable element comprises a flexible diaphragm.
 8. A device according to claim 7 in which said fluid displaceable element comprises a second flexible diaphragm.
 9. A device according to claim 8 in which said means for permitting fluid flow from a source of fluid into said pulse generating chamber comprises a valve means which admits pulses of fluid to said pulse generating chamber when said first diaphragm reciprocates.
 10. A device according to claim 9 in which a second valve means admits pulses of fluid from said pulse generating chamber into said pulse accumulating chamber.
 11. A device according to claim 9 in which said bleed means comprises an opening through said second diaphragm.
 12. A device according to claim 11 in which a poppet is placed at said opening, said poppet having a head which closes said opening when the second diaphragm moves some distance in its path of incremental movement.
 13. A device according to claim 11 including an element moved by said second diaphragm when its incremental movement has been sustained for a time.
 14. A device according to claim 4 in combination with a container comprising a crankcase containing oil and gas above the oil subject to undulating pressure and the means responding to the sustained incremental movement comprises means for terminating operation of equipment creating the undulating pressure.
 15. A liquid level responsive device comprising: a first housing; a first flexible reciprocatable diaphragm crossing the interior of said first housing and creating a first chamber and a second chamber within the housing on opposite sides of the diaphragm; means for introducing pulsating fluid pressures into the second chamber; a first valve through which gas from a source of gas is introduced into the first chamber; a second housing; a second flexible diaphragm crossing the interior of the second housing and creating a first cavity and a second cavity on opposite sides of the second diaphragm within the second housing; a second valve between said first chamber and the first cavity through which pulses of gas pass from the first chamber to the first cavity, said second valve preventing the return of gas from the second cavity to the first chamber thereby causing the second diaphragm to move in one direction in a path of movement when the first diaphragm reciprocates; an actuator movable by substantial uni-directional movement of the second diaphragm in said path of movement; and bleed means at said first cavity for bleeding off gas therefrom, thereby preventing substantial movement of said second diaphragm when said pulsating fluid pressures are weak or unsustained.
 16. A device according to claim 15 in which a fluid pressure sensing duct is in communication with said means for introducing pulsating fluid pressures.
 17. A device according to claim 16 including a switch having a member operated by said actuator.
 18. An undulating fluid pressure responsive device comprising: a reciprocable element having two sides maintained out of communication with each other; means adapted to provide fluid communication between a first of said sides and a body of fluid subject to undulating pressure which can reciprocate said reciprocable element in opposite directions, the other of said sides forming part of the wall of a fluid pulse generating chamber whose volume is changed by the reciprocation; means for developing an output pulse of fluid pressure each time the reciprocable element moves in a first of said directions; means for permitting fluid flow to a delivery region from said pulse generating chamber each time the reciprocable element moves in a second of said directions; a fluid pulse accumulating chamber in communication with said pulse generating chamber to accumulate the generated pulses; valve means between the delivery region and the accumulating chamber preventing the return of fluid from the delivery region to the accumulating chamber; a fluid displaceable element forming part of the wall of the accumulating chamber and bleed passageway means providing communication between said accumulating chamber and said delivery region thereby permitting flow of fluid into said chamber at a rate sufficient to prevent a substantial displacement of said displaceable element when the pulse output of said pulse generating chamber is not both strong and sustained.
 19. A device according to claim 18 in which: the fluid displaceable element undergoes incremental displacements in a path of movement by the fluid pulses applied to it.
 20. A device according to claim 19 in which a movable actuating member is connected to said fluid displaceable element such that a substantial degree of movement of said fluid displaceable element must take place before movement is imparted to said member.
 21. A device according to claim 18 in which the means adapted to provide fluid communication comprises a duct in communication with said first side of said reciprocable element and having a termination adapted to be placed within a container holding a body of liquid and containing a gaseous fluid above the liquid subject to pressure undulations, so that the termination may or may not be submerged in the liquid.
 22. A device according to claim 18 including means providing a pressure bias on at least one side of said reciprocable element.
 23. A device according to claim 18 including means providing a pressure bias against both sides of said reciprocable element.
 24. A device according to claim 21 in which said reciprocable element comprises a flexible diaphragm.
 25. A device according to claim 24 in which said fluid displaceable element comprises a second flexible diaphragm.
 26. A device according to claim 25 in which said means for permitting fluid flow from a source of fluid into said pulse generating chamber comprises a valve means which admits pulses of fluid to said pulse generating chamber when said first diaphragm reciprocates.
 27. A device according to claim 26 in which a second valve means admits pulses of fluid from said pulse generating chamber into said pulse accumulating chamber.
 28. A device according to claim 26 in which said bleed means comprises an opening through said second diaphragm.
 29. A device according to claim 28 in which a poppet is placed at said opeNing, said poppet having a head which closes said opening when the second diaphragm moves some distance in its path of incremental movement.
 30. A device according to claim 28 including an element moved by said second diaphragm when its incremental movement has been sustained for a time.
 31. A device according to claim 21 in combination with a container comprising a crankcase containing oil and gas above the oil subject to undulating pressure and the means responding to the sustained incremental movement comprises means for terminating operation of equipment creating the undulating pressure. 